Field of Invention
Exemplary embodiments of the present invention relate to semiconductor design technology, and more particularly, to a semiconductor memory device and a method of operating the same.
Description of Related Art
Semiconductor memory devices are classified into volatile memory devices and non-volatile memory devices.
A volatile memory device may perform a read/write operation at a high speed, but may lose data stored therein in a non-powered condition. Meanwhile, a non-volatile memory device performs at relatively slow speed in the read/write operation, but may maintain the stored data even when a power is blocked. Accordingly, the non-volatile memory device is used for storing data, which is to be maintained irrespective of being supplied with the power or not. The non-volatile memory devices include a read-only memory (ROM), a mask read-only memory (MROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a phase-change random access memory (PRAM), a magnetic random access memory (MRAM), a resistive random access memory (RRAM), a ferroelectric random access memory (FRAM), and a flash memory. The flash memories are classified into a NOR-type flash memory and a NAND-type flash memory.
The flash memories have an advantage of a random access memory (RAM) for freely programming and erasing data and an advantage of a read-only memory (ROM) for maintaining the stored data even in a non-powered condition. The flash memories have been widely used as a storage medium of portable electronic devices, such as a digital camera, a personal digital assistant PDA, and an MP3 player.
Recently, size of memory cells in the flash memory has reduced and space between the memory cells became narrower. Therefore, threshold voltage distribution of the memory cells may be deteriorated due to interferences between the adjacent memory cells.